Staten Islanders can pocket a few dollars by installing a new front door themselves

A gorgeous front door like this can be installed in one day. You just need to know secret master carpenter ninja tricks. Photo/Tim Carter

Q. My front door is in bad shape, and my wife wants a new one. We visited a showroom and I see that I can purchase a new front door that’s already prehung in the frame. It seems that all I have to do is just nail it in place and I’m good to go. Do you feel I can install a new front door myself? Surely it’s not as simple as just nailing it in place. What tips can you share to help me get this done and save lots of money?

A. Installing a new front door is an ambitious project, especially if you’ve never done it before. That’s not to say you can’t do it. I just want to manage your expectations. Many steps are required to ensure the door works properly, seals tightly to save energy, and that absolutely no water leaks into your home. Water leaks at exterior doors can cause serious structural damage over time.

It’s impossible in this short column to give you all the knowledge I’ve attained about door installation over the years. But I’ll give you a link to a page at my website where you can watch several videos that will really help you get started so you can save money on this job. The money you save by not hiring a contractor can be used to purchase a nicer door.

CHECK MEASUREMENTS

Let’s talk about what can go wrong so you know the pitfalls in this project. For starters, you can make a mistake and buy the wrong door. If your home is less than 50 years old, you should be able to buy a prehung door that fits very nicely in your existing opening. But to make sure that you don’t goof up, you need to check measurements before you get out your credit card.

In my opinion, the easiest thing to do is to remove the interior trim that surrounds the door. You can do this with a razor knife, a wide putty knife and a flat pry bar. Always start at the bottom of the door where the trim meets the door jamb at the floor. Be sure to cut a very fine line with the razor knife where the trim touches the wall surface. This ensures any caulk between the trim and the wall surface doesn’t cause the drywall paper to tear off the wall as you pull the trim away from the wall.

Once the trim is removed, you can see the entire door frame. Use a flashlight if necessary to see where the bottom of the door frame and the threshold assembly touch your concrete slab or the wood subfloor.

Your job is to obtain the outer width and height dimensions of your existing door frame assembly. These are commonly referred to as unit dimensions. It’s critical that your new door match these dimensions as closely as possible. You also want to determine the thickness or width of the door jamb. It’s usually either 4 9/16 inches or 6 9/16 inches. This is the actual thickness of the wall if you measure the width of the wall studs plus the thickness of the interior drywall and exterior wall sheathing.

WHAT YOU’LL NEED

Once you have the new door, you need to make sure you have all the other supplies you need. Don’t start to tear out your existing door unless you have everything on site. You’ll need wood shims, rust-proof trim screws that are at least 2 1/2 inches long, a plastic sill pan flashing kit, rubberized waterproofing membrane, several tubes of elastomeric caulk, and any tools that will help you remove the old door.

The next step, before you start to remove your old door, is to read all the written instructions that come with the new door. Check to make sure all the dimensions are correct. Check to make sure the new door swings the same way as the old door. Be sure you have all the supplies the written instructions call for. You don’t want to remove your old door and find out that you’re missing some critical materials.

The biggest mistake most rookie installers make is installing a new door without a proper flashing under the door. Many feel that a bead of caulk will stop water infiltration. It will not. You need a flashing to keep your house waterproof. I always install a wonderful plastic pre-formed flashing pan under my doors. They come in various sizes to accommodate all doors. It takes just minutes to install this critical component.

Once the new door is in the opening, you want to secure it with the wood shims and the rust-proof fasteners. As you do this, you’re constantly checking to make sure that the door frame is not twisted, that it’s plumb, and that the door threshold is level. If your door doesn’t have glass sidelights, you want to make sure you install a very long screw behind the top door hinge so the door frame is securely fastened to the rough framing. This prevents door droop.

You can watch five free videos showing very important installation steps at my AsktheBuilder.com website. These videos will show you door installation secrets I’ve discovered the hard way over the past 40 years. Go to this page now:

http://go.askethebuilder.com/InstallFrontDoor

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